1. Field of the Invention
The present invention relates to multilayer LC composite components. More particularly, the present invention relates to multilayer LC composite components used in mobile communication apparatuses such as mobile phones.
2. Description of the Related Art
As a conventional multilayer LC composite component of this kind, there is known a multilayer LC filter having a structure as shown in FIG. 12. In a multilayer LC composite component 1, inductor patterns 8 and 9 and resonant capacitor patterns 10 and 11 are provided on a ceramic sheet 5, a ground pattern 12 is disposed on a ceramic sheet 3, a ground pattern 13 is disposed on a ceramic sheet 4, a ground pattern 14 is disposed on a ceramic sheet 6, and a ground pattern 15 is disposed on a ceramic sheet 7.
The ceramic sheets 2 to 7 are stacked to be integrally burned so as to constitute a multilayer body 17 as shown in FIG. 13. The multilayer body 17 includes an input terminal 18, an output terminal 19, and ground terminals G1 and G2. The input terminal 18 is connected to an extended portion 8a of the inductor pattern 8. The output terminal 19 is connected to an extended portion 9a of the inductor pattern 9. The ground terminal G1 is connected to the grounded portions of the inductor patterns 8 and 9 and one end of each of the ground patterns 12 to 15. The ground terminal G2 is connected to the resonant capacitor patterns 10 and 11 and the remaining ends of the ground patterns 12 to 15.
In the above-described LC filter 1, an LC resonator Q1 is defined by an inductor L1 composed of the inductor pattern 8, a resonant capacitor C1 that is defined by arranging the resonant capacitor pattern 10 opposite to the open-circuited end of the inductor pattern 8, and a capacitor C3 that is defined by arranging the inductor pattern 8 opposite to the ground patterns 12 to 15. Similarly, an LC resonator Q2 is defined by an inductor L2 composed of the inductor pattern 9, a resonant capacitor C2 that is defined by arranging the resonant capacitor pattern 11 opposite to the open-circuited end of the inductor pattern 9, and a capacitor C4 that is defined by arranging the inductor pattern 9 opposite to the ground patterns 12 to 15. In addition, in a direction in which the ceramic sheets 2 to 7 are stacked, a pair of the ground patterns 12 and 13 are arranged adjacent to each other above the LC resonators Q1 and Q2, and a pair of the ground patterns 14 and 15 are arranged adjacent to each other below the LC resonators Q1 and Q2.
In the multilayer LC filter, preferably, the widths of the extended portions of the ground patterns are broadened to reduce the inductances of the extended portions. On the other hand, such an arrangement causes separations to occur between the ground patterns and the ceramic sheets. This results from loosen bonds between the ground patterns and the ceramic sheets due to deteriorated contacts between them. Thus, usually, similar to the extended portions 12a to 15a of the ground patterns 12 to 15 shown in FIG. 12, the widths of the extended portions are narrowed and the extended portions are arranged to have a plurality of separate portions.
However, as shown in FIG. 14, the extended portions 12a and 13a of the ground patterns 12 are arranged in the same positions in plan view, and so are the extended portions 14a and 15a of the ground patterns 14 and 15. As a result, magnetic fields generated at the extended portions 12a and 13a converge on the same portions, and the same phenomenon happens to the extended portions 14a and 15a. Thus, in the conventional multilayer LC filter 1, the extended portions of the ground patterns 12 to 15 result in having significantly large inductances. Additionally, openings 16 are formed between the extended portions 12a and 12a and also formed between the extended portions 13a and 13a. However, this arrangement causes a problem in which electromagnetic waves generated inside the LC filter 1 leak to the outside through the openings 16.
Furthermore, when the positions of the extended portions 12a to 15a deviate due to variations occurring in the manufacturing process, the areas of the openings 16 of the ground patterns 12 to 15 change in plan view. Then, the capacitances of the capacitors C3 and C4 composed of the inductor patterns 8 and 9 and the ground patterns 12 to 15 are changed. This causes variations in the filter characteristics of the filter 1.
In order to overcome the problems described above, preferred embodiments of the present invention provide a multilayer LC composite component that minimizes the inductances of ground patterns to prevent electromagnetic waves from leaking outside the component.
According to a preferred embodiment of the present invention, a multilayer LC composite component includes a plurality of insulation layers stacked to define a multilayer body, an inductor and a capacitor arranged in the multilayer body to define LC resonators, at least two ground patterns arranged on two different insulation layers that are adjacent to each other, and the ground patterns arranged above or below the LC resonator in the direction in which the insulation layers are stacked, the two ground patterns electrically connected to an external ground electrode via extended portions respectively, the external ground electrode disposed on the multilayered body, wherein the extended portions of the ground patterns are arranged in different positions in plan view.
In addition, the LC composite component may further include a via-hole connected in the direction in which the insulation layers are stacked to define the inductor, and a capacitor pattern arranged to define the capacitor, in which one end of each inductor is electrically connected to the capacitor pattern of the capacitor defining the LC resonator and the other end of the inductor is electrically connected to the ground pattern.
With the above-described unique and novel arrangement, since the extended portions that are disposed on the different insulation layers are arranged in different positions in plan view, magnetic fields generated at the extended portions do not converge on the same portions. As a result, this arrangement minimizes the inductances of the extended portions.
Furthermore, the extended portions of the plurality of ground patterns may be arranged in a state in which no clearance is left between the extended portions in plan view. This arrangement prevents electromagnetic waves that are generated inside the component from leaking outside.
Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention with reference to the attached drawings.